With the development of wireless communication, a quantity of users continuously increases, and this requires an increased quantity of frequency bands supported by a base station. For reducing costs and a quantity of antennas, that multiple frequency bands share one antenna becomes a trend in the future.
At present, an antenna used by the base station is mainly a dual-polarized antenna. One dual-polarized antenna may support 2R (two-receive), and two dual-polarized antennas may support 4R (four-receive). As shown in FIG. 1A and FIG. 1B, FIG. 1A and FIG. 1B are a schematic diagram of composition of a receiver frequently used in the current base station. The receiver includes two dual-polarized antennas (which support 4R), two power dividers (power splitters), and multiple receive channels (two main receiving channels, two diversity receiving channels, and two inter-frequency channel groups, where each inter-frequency channel group includes N−1 inter-frequency receive channels). Each receive channel includes two same filters, a low noise amplifier, a numerical control attenuator, a frequency mixer, an automatic gain control (English: automatic gain control, AGC for short), and an analog-to-digital converter (English: analog-to-digital converter, ADC for short). For each receive channel, filtering is first performed, by a first filter for the first time, on a radio frequency signal that is received by the dual-polarized antenna; then amplification is performed by the low noise amplifier; then filtering is performed by a second filter for the second time; then attenuation adjustment is performed by the numerical control attenuator; then frequency mixing is performed by the frequency mixer on the radio frequency signal and a local oscillator signal that is output by a local oscillator; then gain adjustment is performed by the AGC; and finally analog-to-digital conversion is performed by the ADC, so that a digital signal is obtained. In FIG. 1A and FIG. 1B, an “Ri filter” represents that a passband of the filter is a frequency band Ri where 1≤i≤N. The receiver may support not only an intra-frequency mode (that is, a frequency band of a signal transmitted on the diversity receiving channel is the same as a frequency band of a signal transmitted on the main receiving channel) but also an inter-frequency mode (that is, a frequency band of a signal transmitted on an inter-frequency channel is different from the frequency band of a signal transmitted on the main receiving channel).
However, the receiver has the following disadvantages: A quantity of frequency bands supported by the base station is increased by mainly increasing a quantity of receive channels (including a diversity receiving channel and an inter-frequency receive channel) in the receiver; however, a larger quantity of receive channels leads to a larger volume of the receiver, and this is unfavorable to miniaturization of the base station; in addition, costs for deploying multiple receive channels are relatively high.